Antlers

Many
animalsincluding goats, sheep and cattlehave horns.
But only a few speciesincluding deer, elk and caribouhave
antlers. Horns are made of dead skin and are permanent. Antlers
are very different: they're made of living tissue that grows and
dies in a yearly cycle. The antlers grow every spring; in early
winter, they die and fall off. You can walk through the woods
and find them lying on the ground. The following spring, the antlers
grow back again, bigger and with more points than before. Some
people think it's possible to tell how old an animal is by counting
the points on its antlers, but the number of points doesn't accurately
correspond to the age of the animal. When antlers are growing,
they are covered with a soft, furry layer of sensitive skin called
velvet. Once the antlers reach full size, the velvet dies
and begins to peel. The animal rubs the dying velvet off against
a tree, leaving the bony core of the antler exposed. That's why
the antlers are worn smoother at the tips than at the base. Antlers,
which are almost always displayed by the male of the species,
are used to establish dominance during the mating season. But
naturalists wonder about the survival value of antlers that are
shed every winter; growing a huge rack of antlers each year requires
a great deal of the animal's energy.